1. Field of the Invention
This invention relates to a method for selective formation of a deposited film, particularly to a selective formation method which forms a deposited film of a desired pattern self-adjustedly.
The method for selective formation of a deposited film according to the present invention may be applicable for, for example, preparation of thin films to be used for semiconductor integrated circuit devices, optical integrated circuit devices, magnetic circuit devices, etc.
2. Related Background Art
As a method for desirably forming a desired deposited film on a desired portion of a desired substrate, there has been heretofore known the deposited film formation method utilizing the photolithographic technique.
FIGS. 1A-1E illustrate an example of the steps showing the method for forming a thin film type deposited film according to photolithography of the prior art.
First, a substrate 101 comprising a material species with a uniform composition as shown in FIG. 1A is washed, and subsequently a thin film 102 is deposited on the whole surface of the substrate 101 according to various thin film deposition methods (vacuum deposition method, sputtering method, plasma discharge method, MBE method, CVD method, etc.) [FIG. 1B].
Subsequently, a photoresist 103 is applied on the thin film 102, [FIG. 1C], the photoresist 3 is exposed to light by use of a photomask of a desired pattern and the photoresist 103 is partially removed by developing [FIG. 1D].
The thin film 102 is subjected to etching with the residual photoresist 103 as the mask to form a thin film 102 of a desired pattern [FIG. 1E].
By repeating such photolithographic steps, thin films of desired patterns are laminated to constitute an integrated circuit. In this case, alignment between the thin films of the respective layers is a very important factor for the characteristics of an element. Particularly, in the case of VLSI where precision of submicron is demanded, the precision of the shape of the thin film of each layer is also extremely important along with alignment.
However, in the thin film forming method of the prior art as described above, it is difficult to effect necessary alignment of the photomask with good precision, and also the precision of the shape is insufficient, because thin films of desired patterns are formed by etching.
FIGS. 2A-2D illustrate another example of the steps showing the method for forming a thin film by use of lift-off of the prior art.
First, a substrate 201 is coated with a photoresist 204, [FIG. 2A], and a photoresist 204 of a desired pattern is removed by photolithography [FIG. 2B].
Subsequently, a thin film 205 is deposited according to the thin film depositing method [FIG. 2C], and the residual photoresist 204 is removed by dissolution. The thin film on the residual photoresist 204 is thereby removed at the same time to form a thin film 205 of a desired pattern [FIG. 2D]. The above steps are repeated to constitute an integrated circuit.
However, such a deposited film formation method performs formation of a deposited film on a photoresist and therefore it is required to perform formation of a deposited film at a temperature not higher than the resistant temperature of the photoresist, whereby the deposition method is greatly restricted. Also, in removing the photoresist, the shape of the residual deposited film is affected thereby to give insufficient precision of shape. Further, there is also a problem such that the possibility of contamination at the side wall portion or inner portion of the deposited film with carbon, etc. which is a component of the photo-resist is high,
On the other hand, as the selective deposition method, it has been known to cover partially a single crystalline substrate with an amorphous thin film and effecting epitaxial growth of the same material as the substrate material selectively only on the exposed portion of the single crystalline substrate. For example, there are the selective epitaxial growth (SEG) method in which silicon is selectively grown with partial coverage of a single crystalline silicon substrate with silicon oxide (B. D. Joyce & J. A. Baldrey, Nature, vol. 195, 485, 1962), the method in which epitaxial growth of GaAs is selectively effected with coverage of a GaAs substrate with an amorphous thin film such as of SiO.sub.2, Si.sub.3 N.sub.4, etc. (P. Rai-Choudhury & D. K. Schroder, J. Electrochem. soc. 118, 107, 1971), etc.
However, according to these selective deposition methods, since the same kind of single crystalline semiconductor is selectively grown on the exposed surface of the single crystalline substrate, the deposition surface for the ground is limited to the single crystalline semiconductor, and they are not applicable for insulating substrates.